Tom Brady is one of the greatest quarterbacks in NFL history. In many eyes, he's the best to ever do it. As he prepares to enter his 21st season in the league, he may test the free agent waters for the first time in his career. While the New England Patriots would love to have him back, things are far from final at this point and there's a real chance Brady plays elsewhere in 2020.

With that said, what's the market for an aging all-time great look like? There have been rumors here and there centered around teams willing to offer Brady close to $30 million per year for his services, but nothing legitimate has materialized. NFL Network's Michael Giardi recently did a segment on what those around the league think about Brady at this point in his career.

There are two main takeaways from the video. First and foremost, Tom Brady's supporting cast certainly didn't do him any favors in 2019. He didn't have the protection and weapons he used to, which certainly played a factor in his performance. Secondly, executives around the league believe Brady is still good at his job, but they're worried about his ability to hold up long-term.

Brady has suffered numerous minor injuries over the past several seasons, ranging from his elbow, to his knee, to his foot. He'll be 43 by the start of next season. Giardi points out that injuries don't go away at that age — they become worse. Brady's been able to fight off anything serious, but that may not last much longer.

There are also some other concerns to take into account. From a statistical perspective, Tom Brady regressed in 2019. He averaged his lowest yards-per-attempt since 2002. The last full season in which he threw just 24 touchdowns: 2006. His passer rating has declined in each of the last three seasons. The Brady NFL fans grew to love is no longer.

The last variable to consider: supporting cast. While Brady didn't have an embarrassment of riches on the offensive side this past season, he had a top defense and one of the best head coaches the league has ever seen. If he leaves New England, will he fall into a situation similar to the one he's been in for two decades? That could affect his play in a major way.

None of this is to say that Brady is completely washed. After all, most quarterbacks wish they could play at age 43. It's long been a goal of Brady's to last until age 45 in the NFL, so that means he's got a few more seasons left to finish. He's got the accolades. He's got the numbers. Could the final thing on his career checklist be to prove his worth without the support of Bill Belichick?

If that's the case, teams should be cautiously optimistic when courting Brady in free agency. He's not the Tom Brady of 10 (or even five) years ago. Front office personnel must be able to distinguish between those different versions of a historically good quarterback if they want to succeed.